"This delay makes it unlikely that the purpose of the error detection that we discovered in the ACC is to correct actions as they take place," said Schall.
An influential theory about ACC function has suggested that the brain is sensitive to the conflict that arises when tasks are too complex and subjects are being asked to do more than they can without making errors. Schall's earlier work on the supplementary eye field found neurons signaling this conflict, but they failed to find neurons signaling conflict alone in the ACC. This observation is at odds with certain functional brain imaging studies in humans.
These results do not mean that the ACC does not also monitor conflicts, Schall cautions. Virtually all of the human measurements have been made using tasks that involve button pushing or other manual tasks, rather than eye movements. The ACC has no direct connections to the areas of the brain that control the eyes but it does have direct connections to those that control the muscles in the hands and arms. So hand movements may be controlled differently than eye movements. There is also the possibility that the ACC in humans may function differently than it does in monkeys.
"These results are telling us that things are not as simple as some people have thought," says Paus, who adds that we won't really be able to tie these signals back to cognitive functions until researchers can go beyond the current stage of simply recording brain activities to that of actually inducing changes in brain activity either through the administration of drugs or electrical stimulation to small groups of neurons and observing the changes in beha
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Contact: David F. Salisbury
david.salisbury@vanderbilt.edu
615-343-6803
Vanderbilt University
2-Oct-2003